Batch and fixed bed studies: Removal of copper(II) using chitosan

73
Sustain. Environ. Res., 25(2), 73-81 (2015)
Batch and fixed bed studies: Removal of copper(II) using
chitosan-coated kaolinite beads from aqueous solution
I-Ping Chen,1 Chi-Chuan Kan,2 Cybelle Morales Futalan,3 Mary Jane C.
Calagui,4 Shiow-Shyung Lin,1 Wan Chi Tsai5 and Meng-Wei Wan1,*
1
Department of Environmental Engineering and Science
Chia Nan University of Pharmacy and Science
Tainan 71710, Taiwan
2
Institute of Hot Spring Industrial
Chia Nan University of Pharmacy and Science
Tainan 71710, Taiwan
3
Department of Environmental Engineering
University of the Philippines-Diliman
Quezon City 1101, Philippines
4
College of Chemical Engineering
Cagayan State University
Cagayan 3500, Philippines
5
Department of Medical Laboratory Science and Biotechnology
Kaohsiung Medical University
Kaohsiung 80708, Taiwan
Key Words: Breakthrough curve, chitosan, fixed bed, groundwater, kaolinite
ABSTRACT
In this study, Cu(II) removal under batch and fixed-bed conditions using chitosan-coated kaolinite
(CCK) was investigated. The surface morphology of CCK was characterized using scanning electron
microscopy. Batch experiments showed that 1:20 chitosan to kaolinite ratio can provide satisfactory
Cu(II) removal. Kinetics study revealed that adsorption is best described by pseudo-second order
equation (R2 > 0.99). The isotherm data of Cu(II) adsorption using different ratios of CCK fitted well
with Langmuir model (R2 > 0.98). The Langmuir constant, qmL has the following values of 11.2, 9.4 and
8.9 mg g-1 for 1:5, 1:10 and 1:20 chitosan to kaolinite ratio. In fixed bed studies, Cu(II) uptake increases
and longer breakthrough time are attained as pH becomes more acidic. In addition, about 93% of Cu(II)
removal from real groundwater system was attained using 2 g CCK.
INTRODUCTION
Copper, an essential mineral needed by the human
body, is generated by several anthropogenic sources
such as cooling water systems, mining, fungicide
manufacturing, metal electroplating and finishing [1].
An increase in Cu(II) intake can cause health problems
like Wilson’s disease, gastrointestinal disturbance,
vomiting, and lesions in the central nervous system
[2,3]. In addition, heavy metal contamination in
surface water and groundwater will further prevent any
beneficial use of the water bodies.
Among the physicochemical treatment for heavy
metal removal, adsorption has the ability to remove
contaminants in wastewater with high solute loading
*Corresponding author
Email: peterwan@mail.cnu.edu.tw
and even at dilute concentrations [4]. However, using
commercialized adsorbent such as activated carbon
is considered to be expensive, which leads to high
operational costs [5]. On the other hand, chitosan
has been proven to have the highest metal chelating
capacity among natural adsorbents [6]. Chitosan,
polyβ(1→4)-2-amino-2-deoxy-ᴅ-glucose, is produced
through deacetylation of chitin using a strong alkaline
solution [7]. Due to its hydrophilicity, it becomes soft
and gel-like in aqueous media [4]. In addition, it easily
swells and crumbles and has a low specific surface area
[1,8]. Modification could be applied to chitosan in order
to improve its chemical and mechanical properties.
Physical modification such as coating chitosan on a
support material would enhance the accessibility of
74
Chen et al., Sustain. Environ. Res., 25(2), 73-81 (2015)
its binding sites and improve its mechanical stability
[9,10].
Clay materials are made up of the colloidal
fraction (< 2 μm) from soils, sediments and rocks
[11]. They are abundant, cheap and have relatively
large surface areas [12], which makes clay minerals
an attractive support or immobilization material for
chitosan. Kaolinite has a 1:1 aluminosilicate structure,
which is the most abundant phyllosilicate mineral
found from weathered soils [13]. Recent studies have
been carried out on chitosan-bentonite or chitosanmontmorillonite composites in the removal of tannic
acid [14], heavy metals [15-20], tungsten [21] and dyes
[22]. Only a few batch studies have been performed
on chitosan-coated kaolinite (CCK) in the removal of
copper [23]. In addition, no fixed bed studies or studies
utilizing real groundwater have been carried out on
copper removal using CCK.
In continuation of the work made by Kan et al.
[23] the removal of Cu(II) using CCK from aqueous
solution under batch and fixed bed conditions was
studied. The effect of initial concentration and ratio of
chitosan to kaolinite on Cu(II) removal and adsorption
capacity was investigated. Kinetic experimental data
were analyzed using pseudo-first and pseudo-second
order equation. Equilibrium data were evaluated
using Langmuir and Freundlich isotherm. Fixed bed
studies examined the effect of pH on the shape of the
breakthrough curve.
MATERIALS AND METHODS
1.Chemicals
(FTIR, Jusco FTIR-410) with a disc composing of 1:10
ratio of sample to KBr.
3.Preparation of CCK Beads
The procedure applied is similar to the method
used by Wan et al. [9] with slight modifications, where
the chitosan to kaolinite weight ratio (5:100, 5:50,
5:25) was varied.
In order to prepare 1:20 chitosan to kaolinite
ratio, chitosan (5 g) was dissolved in 5% (v/v) HCl by
stirring at 300 rpm for 2 h. Kaolinite (100 g) was added
into the chitosan solution and stirred for another 3 h.
Drop wise addition of 1 N NaOH was carried out to
precipitate chitosan onto kaolinite particles. CCK beads
were washed with deionized water and dried in an oven
(Channel Precision Oven model DV452 220V) for 24 h
at 65 °C. CCK beads with heterogeneous size range of
0.35-0.71 mm were used throughout the study.
4.Comparative Study of Different Adsorbents
Adsorption of Cu(II) using chitosan, kaolinite
and CCK (1:20, 1:10, 1:5) was carried out using batch
experiments. About 2.5 g adsorbent and 30 mL Cu(II)
solution were agitated using a reciprocal shaker bath
(YIH BT350) for 4 h with initial pH 4 at 25 °C. The
Cu(II) residual was analyzed using inductively-coupled
plasma spectrometry (ICP-OES Perkin Elmer Optima
DV2000). The adsorption capacity, q e (mg g -1) is
computed using Eq. 1:
qe =
(C0 − Ce ) V
m
(1)
Low molecular weight chitosan (75-85%
deacytelation degree) and kaolinite (Al2Si2O5OH4) were
procured from Sigma Aldrich. CuSO4 (99% purity),
NaOH (99% purity) and HCl (37% fuming) were
purchased from Merck (Germany).
where V is the volume of solution (mL), m is the mass
of adsorbent (g), C0 and Ce is the initial and equilibrium
Cu(II) concentration (mg L-1).
2.Instrumentation
Kinetic studies were carried out by placing 2.5 g
adsorbent in contact with 30 mL Cu(II) solution under
agitation speed of 50 rpm at 25 °C. Samples were
taken at pre-determined time intervals (15 to 240 min).
Equilibrium studies were performed by agitating 2.5 g
adsorbent and 30 mL Cu(II) solution using 50 rpm at
25 °C for 24 h under varying initial concentrations (100
to 2000 mg L-1).
The average pore diameter and surface area of
chitosan, kaolinite and CCK were measured utilizing a
BET multipoint technique and gas adsorption surface
analyzer (GEMINI 2360 Micrometrics) using the
adsorption-desorption isotherm of N2 at 77 K.
The surface morphology of chitosan, kaolinite
and CCK was analysed with a scanning electron
microscopy (SEM, S-3000N Hitachi) under a vacuum
running at 20 kV and using a tungsten filament. The
samples were coated with a thin layer of gold (10 nm)
using a sputter coater.
CCK beads before and after Cu(II) adsorption were
analysed using fourier transform infrared spectroscopy
5.Kinetic and Isotherm Studies
6.Fixed Bed Study
Fixed bed experiment was performed using a
UPVC column with internal diameter of 3 cm and
length of 30 cm. The fixed bed was packed with 9 g
CCK (1:20) and bed height of 3 cm. The fixed bed
Chen et al., Sustain. Environ. Res., 25(2), 73-81 (2015)
was operated in a downflow mode, where 200 mg L-1
Cu(II) solution was pumped at the top of column under
constant flow rate of 5 mL min-1. The initial solution
pH was adjusted in the range of pH 3 to 4 using 0.1 M
HCl or 0.1 M NaOH.
The adsorption capacity at breakthrough point, qbrk
is described as when Cu(II) in effluent reaches 10% of
influent concentration. It is given by:
(2)
where M is adsorbent mass of fixed bed (g), mbrk is
the total amount of Cu(II) adsorbed by column at
breakthrough point (mg), Q is the flow rate (mL min-1)
and tb is time at breakthrough (min). The adsorption
capacity at exhaustion (qexh) corresponds to amount of
Cu(II) contained in fixed bed when effluent reaches
90% of influent concentration. It is computed using [5]:
q exh
m
= exh
M
(3)
where mexh is the total quantity of Cu(II) adsorbed by
column until exhaustion. It is calculated using Eq. 4:
(4)
where te is exhaustion time (min), and Ct is the effluent
concentration (mg L-1) at time t. The treated effluent
volume is calculated using Eq. 5:
(5)
Veff = Q te
The length of mass transfer zone or MTZ, Zm could
be calculated using Eq. 6:
 tb 
Zm = Z 1 − 
 te 
(6)
where Z is the bed height (cm).
The total amount of Cu(II), mtotal (g) applied to
the column and total solute removal percentage can be
calculated using Eqs. 7 and 8 [24]:
mexh
%removal =
mtotal
100
(7)
(8)
7.Adsorption of Cu(II) from Groundwater
Batch experiments were performed using aqueous
solution and real groundwater. Groundwater was
obtained from a monitoring well located in Chia Nan
University of Pharmacy and Science (Taiwan). The
chemical composition of the groundwater is listed in
75
Table 1. The pH of the aqueous solution was adjusted
to pH 8.12, which is similar to the pH of groundwater.
Both aqueous solution and groundwater were spiked
with 3 mg L-1 Cu(II) and the removal capacity of CCK
(1:20) was studied under varying adsorbent mass.
RESULTS AND DISCUSSION
1. Surface Morphology
As shown in Fig. 1, the SEM micrograph revealed
that the texture of CCK (1:20) is denser and shows sign
of aggregation in comparison to the surface of chitosan
and kaolinite. The aggregated structure could be
attributed to the hydroxyl and amine groups of chitosan
forming hydrogen bonds with the silicate hydroxylated
edge groups of kaolinite [25].
2. Surface Area Analysis
In Table 2, the surface area, pore volume and
average pore diameter of chitosan, kaolinite and
CCK are listed. Based from the International Union
of Pure and Applied Chemistry classifications, the
pore diameters are divided into three categories:
macropores (d > 50 nm), mesopores (2 nm < d < 50
nm) and micropores (d < 2 nm). The results show that
chitosan, kaolinite and CCK are mesoporous materials.
From Table 2, chitosan exhibited the least surface area
whereas kaolinite provided the largest surface area. In
comparison to chitosan, physical modification such as
coating chitosan onto kaolinite led to an improvement
of the surface area and pore volume. However, the
properties of CCK such as surface area, pore volume
Table 1. Chemical characteristics and background composition of groundwater
Parameter
Value
pH
8.12
-1
Conductivity (µS cm )
2480
Eh (mV)
75
Dissolved oxygen (mg L-1)
1.4
Alkalinity (ppm as CaCO3)
680
Total organic carbon, TOC (mg L-1)
5.2
Ion species:
Total arsenic (µg L-1)
11.9
Chloride (mg L-1)
246
Sulfate (mg L-1)
34
-1
Nitrate (mg L )
0
Phosphate (mg L-1)
1.6
-1
Potassium (mg L )
34
Calcium (mg L-1)
24
-1
Sodium (mg L )
625
Heavy metals:
Iron (mg L-1)
0.51
Manganese (mg L-1)
0.15
Lead (mg L-1)
0.37
-1
Nickel (mg L )
0.68
Copper (mg L-1)
3.0
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Chen et al., Sustain. Environ. Res., 25(2), 73-81 (2015)
4. Effect of Initial Concentration
Fig. 1. SEM micrographs of (a) kaolinite, (b) chitosan and
(c) CCK (1:20).
Table 2. Surface area and pore characteristics of adsorbent
beads analyzed by BET N2 adsorption-desorption
analysis
Adsorbent
Chitosan
Kaolinite
CCK
Surface area
(m2 g-1)
0.04
6.8
4.1
Pore volume
(m3 g-1)
< 0.0001
0.0108
0.0070
Average pore
diameter (nm)
11.5
5.2
5.0
and average pore diameter decreased in comparison to
kaolinite. It implies that individual kaolinite particles
are not coated by chitosan. Instead, aggregates of
kaolinite were coated by the chitosan polymer. The
results are similar to the study of Monvisade et al. [22],
where decrease of pore volume of chitosan intercalated
montmorillonite was attributed to the blocking of
montmorillonite pores upon coating with chitosan [22].
3. FTIR Analysis
The FTIR spectra of the CCK before and after
Cu(II) adsorption of EBT are shown in Fig. 2 and Table
3. The hydroxyl (-OH) stretching vibration is attributed
to the band at 3674 cm-1. The bands at 948 and 835
cm-1 correspond to the -Si-OH and -Al(OH)3 stretching
vibrations. In the amine functional groups, the peak at
3412 cm-1 indicates -N-H2 stretching while band around
1047 cm-1 is attributed to -C-N stretching. On the other
hand, the peak at 1657 cm-1 refers to the -N-H2 stretching in amide group. After Cu(II) adsorption, the peaks
at 3412 and 1047 cm -1 shifted to higher wavelength
of 3426 and 1070 cm -1 that indicates the -NH 2 and
-C-N groups were involved in the removal of Cu(II).
Meanwhile, the peak at 1657 cm-1 shifted to lower
wavelength of 1550 cm-1, which indicates that -NH2
from amide functional group is also involved in
the adsorption of Cu(II). However, there were no
significant changes or shifts observed in the region of
3674, 948 and 835 cm-1, which implies that hydroxyl
groups are not involved in the removal of Cu(II).
Figure 3 shows the adsorption capacity and percent removal of adsorbents under varying initial concentration. The percent Cu(II) removal was observed to
decrease with increasing initial concentration, which
is caused by saturation of binding sites at higher
concentration. On the other hand, adsorption capacity
increases as initial concentration was increased from
100 to 2000 mg L -1. A high concentration gradient
serves as an important driving force that will help
overcome the mass transfer resistance of Cu(II)
between liquid and solid phases [26]. Among the
adsorbents, chitosan and kaolinite provided the highest
and lowest removal efficiency and adsorption capacity,
respectively. It was observed that CCK beads have
better removal efficiency and adsorption capacity than
kaolinite, where increasing the amount of chitosan
coated on kaolinite would result in removal efficiency
similar to that of chitosan.
5. Effect of pH
In Fig. 4, the effect of pH on the Cu removal
efficiency and adsorption capacity of CCK on Cu(II)
removal is illustrated. As the pH was decreased from
7 to 2, the Cu(II) removal efficiency and adsorption
capacity were observed to decrease. This could be due
to the higher amount of H+ present in acidic solution,
which competes with Cu(II) for the binding sites of
CCK. In addition, a lower pH indicates that more
amine groups become protonated (-NH 3 + ), where
positively charged amine groups exert an electrostatic
repulsive force to the approaching Cu(II) ions on the
CCK surface.
6. Kinetics Study
In order to determine the rate of Cu(II) uptake of
CCK beads, kinetic models such as pseudo-first order
and pseudo-second order equation were applied to the
experimental data. The pseudo-first order equation is
given by Eq. 9:
log(qe − qt ) = log qe −
k 1t
2.303
(9)
where qe and qt refer to Cu(II) adsorbed by CCK (mg
Table 3. FT-IR analysis of CCK (before and after copper adsorption)
Frequency (cm-1)
IR peak
Before adsorption
After adsorption
Differences
1
3674
3674
0
2
3412
3426
+14
3
1657
1550
-107
4
1047
1070
+23
6
948
945
-3
7
835
834
-1
Assignment
-O-H stretching
-N-H2 stretching
-N-H2 bending
-C-N stretching
-Si-OH stretching
-Al(OH)3 stretching
Chen et al., Sustain. Environ. Res., 25(2), 73-81 (2015)
77
Fig. 4. Effect of pH on the percent (%) removal and adsorption capacity of CCK in the removal of Cu(II)
from aqueous solution.
Fig. 2. FT-IR spectra of pure CCK and CCK loaded with
Cu(II).
This indicates that the rate-determining step of Cu(II)
adsorption onto CCK is chemisorption. The pseudosecond order rate constant k2 obtained for CCK (1:20)
is slightly lower than the values for CCK (1:10, 1:5).
This implies that rate of adsorption is slightly higher
for CCK (1:5, 1:10) over CCK (1:20), which led to
better adsorption capacity.
7. Isotherm Study
In this study, Langmuir and Freundlich models
are applied to the equilibrium data. The Langmuir
model assumes occurrence of monolayer coverage
and no transmigration of adsorbate takes place on the
adsorbent surface [28]. The Langmuir equation is given
as:
qe =
Fig. 3. Behavior of Cu(II) in terms of percent removal and
adsorption capacity using chitosan, kaolinite and
CCK (1:5, 1:10, 1:20).
g-1) at equilibrium and time t, and k1 is the pseudo-first
order kinetic rate constant (min-1) [27].
The pseudo-second order equation is shown in Eq.
10:
t
1
k 2 qe
t
=
+
2
q
q
t
e
(10)
where k2 (g mg-1 min-1) is the rate constant [7].
As shown in Table 4, the adsorption of Cu(II)
using CCK correlates well with pseudo-second order
equation due to high correlation coefficient values (R2
> 0.991). In addition, a good agreement was observed
between theoretical qe values generated by the pseudosecond order equation and experimental q e values.
qmaxb Ce
1 + b Ce
(11)
where q max is the maximum adsorption capacity of
Cu(II) at complete monolayer coverage (mg g-1) and b
refers to the affinity of Cu(II) to the binding sites (mL
mg-1) [29]. The linearized form is provided in Eq. 12:
1
1
1
=
+
qe qmax b qmaxCe
(12)
The Freundlich model is based on assumption of
reversible adsorption of a heterogeneous system [7]. It
is given by Eq. 13:
1
log qe = log K F + log Ce
n
(13)
where KF and n are Freundlich constants that refer to
the adsorption capacity (mg g -1) and heterogeneity
factor, respectively.
Based from Table 5, CCK beads of ratio 1:20, 1:10
and 1:5 correlated well with the Langmuir model given
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Chen et al., Sustain. Environ. Res., 25(2), 73-81 (2015)
Table 4. Kinetic parameters of Cu(II) adsorption using CCK (1:20), CCK (1:10) and CCK (1:5)
Pseudo-first order
Pseudo-second order
Experimental qe
k2
Adsorbent
C0 (mg L-1)
-1
2
-1
k1 (min )
R
qe (theo)
R2 qe (theo)
(mg g )
(g mg-1 min-1)
CCK (1:20)
100
1.2
0.19
0.64
2.4
0.12
0.99
1.3
500
5.4
0.16
0.74
2.9
0.10
0.99
5.3
1000
8.5
0.10
0.77
4.0
0.07
0.99
8.8
2000
9.4
0.09
0.60
4.1
0.07
0.99
9.5
CCK (1:10)
100
1.2
0.21
0.61
2.6
0.14
0.99
1.4
500
6.0
0.19
0.62
3.1
0.12
0.99
6.1
1000
11
0.15
0.76
3.8
0.08
0.99
11
2000
13
0.12
0.56
4.3
0.09
0.99
14
CCK (1:5)
100
1.2
0.21
0.62
3.3
0.14
0.99
1.4
500
6.0
0.19
0.72
3.9
0.13
0.99
6.3
1000
12
0.17
0.76
4.5
0.09
0.99
12
2000
23
0.10
0.64
5.6
0.06
0.99
23
by high correlation coefficient values (R 2 > 0.987).
Based on qmax, the order of adsorption is in the order:
CCK (1:5) > CCK (1:10) > CCK (1:20). It is observed
that as the amount of chitosan coated on kaolinite increases, qmax value increases as well. In terms of Langmuir coefficient, b, CCK (1:5) and CCK (1:20) provided the highest and lowest value, respectively. The coefficient b describes affinity of Cu(II) to the binding
sites of CCK, indicating that Cu(II) has high affinity to
be adsorbed onto CCK (1:5) over CCK (1:20) due to
higher number of binding sites available on CCK (1:5).
A dimensionless constant separation factor, R L
could be calculated from Langmuir isotherm model,
given by:
(14)
The values of RL would indicate whether isotherm
is irreversible (RL = 0), favorable (0 < RL < 1), linear (RL
= 1) or unfavorable (RL > 1). Based from Table 5, the
RL values indicate that Cu(II) adsorption onto CCK,
irrespective of the amount of chitosan in kaolinite, is
favorable.
Table 6 lists the adsorption capacity of CCK, modified chitosan forms and other biosorbents. In this study,
CCK attained a good maximum adsorption capacity,
which is higher in comparison to bentonite, chitosancoated sand, chitosan immobilized on bentonite, coconut shell, bark and sugarcane [20,30-32].
8. Fixed-bed Study
The effect of initial solution pH on the shape of
the breakthrough curve is shown in Fig. 5. The flow
rate, initial inlet concentration and bed height are kept
constant at 5.0 mL min-1, 200 mg L-1 and 3 cm. An
increase in initial pH from 3 to 4, the time to reach
breakthrough and exhaustion was observed to increase
as well. The breakthrough curve becomes steeper at pH
4, resulting in a quick exhaustion of the fixed bed. A
longer breakthrough and exhaustion time of 70 and 130
min was observed to occur under pH 3 while shorter
breakthrough and exhaustion times at 40 and 110 min
took place at pH 4.
Table 7 lists the calculated column parameters such
as qbrk, qexh, % removal, Zm and Veff. As the pH becomes
more acidic from pH 4 to 3, the Veff was observed to
increase. Correspondingly, the parameters such as qbrk,
qexh and % removal increased while Zm decreased at
pH 3. However, other studies about chitosan and its
derivatives regarding the effect of pH show that Cu(II)
Table 5. Langmuir and Freundlich parameters and correlation coefficient of CCK beads
Langmuir
Adsorbent
b
qmax
R2
RL
1/n
CCK (1:20)
1.78
8.9
0.99
0.0033
0.20
CCK (1:10)
2.25
9.4
0.99
0.0044
0.25
CCK (1:5)
3.01
11
0.98
0.0056
0.38
Table 6. Comparison of the adsorption capacity of Cu(II) ions onto various bioadsorbents
Adsorbent
Adsorption capacity (mg g-1)
CCK
8.9
Bentonite
7.9
Coconut shell
2.6
CCB (chitosan-coated bentonite)
12.2
CIB (chitosan immobilized on bentonite)
9.9
CCS (chitosan-coated sand)
8.8
Kudzu, bark
8.2
Sugar cane
0.3
Freundlich
KF
2.20
3.02
3.72
R2
0.96
0.93
0.98
Reference
This study
[29]
[30]
[19]
[31]
[20]
[30]
[30]
Chen et al., Sustain. Environ. Res., 25(2), 73-81 (2015)
Fig. 5. Breakthrough curves of Cu(II) under different
initial solution pH (pH 3-4).
Table 7. Column parameters of CCK under varying initial
solution pH
Initial
Veff
qb
qe
% Cu(II)
Zm
pH
(mL) (mg g-1) (mg g-1) removal (cm)
pH 3
650
7.3
9.9
69
1.38
pH 4
550
4.2
6.3
52
1.91
*Bed height = 3 cm; Q = 5 mL min-1; C0 = 200 mg L-1
removal using grafted chitosan with poly(acrylamide)
[33], chitosan coated PVC beads [4] and H 2 SO 4
modified chitosan [7] decreases as the pH becomes
more acidic. In this study, pH 3 showed better Cu(II)
removal and adsorption capacity over pH 4. This could
be attributed to excess Cl- ions present, where HCl was
added to adjust to pH 3. A high Cl- concentration could
lead to formation of Cu(II) complexes, where Cl- acts
as a bridging ligand, connecting two or more Cu(II)
together [9]. Complex formation of Cu(II) causes an
increase in removal and adsorption capacity since each
binding site of CCK would retain more than one Cu(II)
ion.
9.Adsorption of CCK (1:20) in Real Groundwater
Figure 6 shows the Cu(II) removal capacity of
CCK from groundwater and aqueous solution under
varying adsorbent mass. In both aqueous solution
and groundwater, removal of Cu(II) increases with
increasing mass of adsorbent from 0.02 to 2 g, due
to greater number of available binding sites on
CCK. The maximum removal of > 99 and 93% was
achieved using 2 g CCK for aqueous solution and
groundwater, respectively. At pH 8.12, the removal
of Cu(II) in aqueous solution and real groundwater
could be attributed due to a combination of Cu(OH)2
precipitation and adsorption of Cu(II) by CCK beads.
79
Fig. 6. Percentage removal of Cu(II) using CCK (1:20)
from aqueous solution and real groundwater
system.
Experiments were carried out without the addition of
CCK, where precipitation is attributed in removing 17
and 22% of Cu(II) in aqueous solution and groundwater,
respectively. However, it could be observed that the
percentage removal of Cu(II) was higher in aqueous
solution in comparison to the groundwater. This is
attributed to background cations present in groundwater
such as Pb(OH)+, Ni2+, Mn2+ and Fe(OH)2+ that could
compete for the available binding sites on CCK.
CONCLUSIONS
Results of the study showed that CCK (1:20) can
be used as an adsorbent in removing Cu(II) under batch
and fixed bed conditions. The kinetic data correlated
well with the pseudo-second order equation, signifying
chemisorption as the rate-determining step. Isotherm
data were best described using the Langmuir model.
The adsorption capacity for Cu(II) under varying
chitosan to kaolinite ratio can be arranged in the order:
1:5 > 1:10 > 1:20. In fixed bed study, high Cu(II)
removal and longer breakthrough time were attained at
pH 3. In addition, a maximum Cu(II) removal of > 99
and 93% can be achieved using 2 g CCK from aqueous
solution and real groundwater system, respectively.
Conclusively, CCK is a possible material to be used as
an adsorbent in a permeable active barrier system in the
treatment of contaminated groundwater.
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Discussions of this paper may appear in the discussion section of a future issue. All discussions should
be submitted to the Editor-in-Chief within six months
of publication.
Manuscript Received: December 5, 2013
Revision Received: March 24, 2014
and Accepted: June 3, 2014